1. Field of the Invention
The present invention relates to a new type of phosphorus containing epoxy resin compositions with flame retardant and a resin sheet resin clad metal foil prepreg laminated board multi layer board used for an electric circuit board containing said epoxy resin.
2. Description of the Prior Art
To copper clad laminates, which are in use for electronic or electric apparatus and devices, the measures such as fire prevention or retardation are strongly required. Therefore, halogenated epoxy resins that have flame retardance are usually in use for copper clad laminates. Especially, among halogen group of atoms, by introducing bromine into epoxy resin, an excellent flame resistance can be provided to the epoxy resin and its cured product that has highly reactive epoxy groups and characteristics can be obtained, therefore, the halogenated epoxy resins, especially brominated epoxy resins are known to useful material for electronic or electric devices. However, when these halogenated epoxy resin are used at high temperatures for a long term, they can be dissociated to form halogen compounds such as hydrogen halogenide and halogen, and subsequently might be a danger to occurring corrosion problem for wires, and such actual accidents have been already reported. Furthermore, it is pointed out that toxic chemical substances such as dioxin and hydrogen halogenide could be formed to incur a serious environmental problem when used parts of electric and (or) electronic devices are calcined. This indicates that use of halogen containing flame retardant could result in such environmental problem. Considering the present situation of epoxy resin composition, the research to develop a new epoxy resin composition substitute for halogenated epoxy resins is highly required. Under the current situation, the development and commercialization of a flame retardant epoxy resin not containing any halogen and a copper clad laminated for printed wiring applications using that said flame retardant epoxy resin can be said as a subject to meet the current requirement of the era.
The inventors of this invention have studied intensively to develop a new type of flame retardant epoxy resins not containing any halogen and a copper clad laminate for printed wiring applications using said flame retardant epoxy resin, and aimed a basic theory of flame retardance by phosphorus and phosphorus compound disclosed in pages 49, 52-59 of xe2x80x9cFlame Retardation of Polymerxe2x80x9d (published by Taiseisha, 1989, Tokyo, Japan. Hitoshi Nishizawa). And the inventors of this invention have found that the new flame retardant phosphorus containing epoxy resin composition that said basic theory is applicable to can be obtained only by the use of a specific organic phosphorus compound, and furthermore, the resin compositions obtained by containing specific epoxy resin as an essential component indicate an excellent flame retardance, and physical properties of its cured products are suitable for printed wiring applications. Thus, we accomplished the present invention.
As disclosed in EP0806429A2, the flame retardant epoxy resin not using any halogen, which is a phosphorus containing organic compounds with epoxy groups, which are prepared from organic phosphorus compounds and epoxy resins have been investigated; however, when bifunctional epoxy resins are used as starting material, the concentration of epoxy group, which is a reactive functional group, will become lower, and lowering of heat resistance of the hardened epoxy resin is pointed out as a problem. Furthermore, for example, the viscosity of a phosphorus containing epoxy resin obtained from organic phosphorus compounds and epoxy resins, which has been disclosed in JP4-11662A, is too high to use it hence, it is required to decrease in actual viscosity by adding another liquid epoxy resin with lower viscosity. Therefore, generally the epoxy resin compositions using this kind of epoxy resin has a problem that the phosphorus content will be lowered in the composition. An epoxy resin containing phosphorus disclosed in JP11-166035A can be obtained from an organic phosphorus compound and epoxy resins, however, this has a problem to decrease in heat resistance and adhesion.
The present invention is aimed to solve the above mentioned problem, and the a im of this invention is to provide a flame retardant epoxy resin composition that contains phosphorus and epoxy groups having excellent flame retardance, heat resistance and adhesion which is useful for printed wiring applications, including a resin sheet, resin clad copper (RCC), prepreg, copper clad laminate and build-up wiring board.
That is, the important point of this invention is a phosphorus containing epoxy resin compositions, comprising an epoxy resin composition (a) in which a phosphorus containing epoxy resin (A) and a hardener are contained, wherein the said phosphorus containing epoxy resin (A) is a phosphorus containing resin compositions prepared by reacting phosphorus containing organic compounds (B) obtained by the reaction in the range of molar ratio of 1.01 to 2 moles of organic phosphorus compounds (b) having one active hydrogen atom bonded to phosphorus atom with 1 mole of quinone compounds, with at least one kind of epoxy resins (C) selected from the group composed of general formula 1, general formula 2 or general formula 3 so as the content of the said epoxy resins (C) to be from 20 to 45 wt. %,
The other composition of this invention, using of novolac type epoxy resins for such as kind of epoxy resin (C) and the above mentioned epoxy resin (A) is prepared by reacting phosphorus containing organic compounds (B) obtained by the reaction in the range of molar ratio of greater than 0 mole to smaller than 1 mole of quinone compounds with 1 mole of organic phosphorus compounds (b) having one active hydrogen atom bonded to phosphorus atom, with novolac type epoxy resin so as content of the said epoxy resin (C) to be more than 20 wt. %. Furthermore, the another important point of this invention is a flame retardant epoxy resin composition containing a phosphorus with epoxy resin characterized by using the said phosphorus containing epoxy resin compositions and total content of phosphorus in whole resin composition is in the range of 0.5 to 4 wt. %. 
wherein R1is a hydrogen atom and/or a phenyl group, m is an integer including 
wherein R2 is a hydrogen atom and/or a phenyl group, n is an integer including 0, 
wherein R3 is a hydrogen atom and/or a phenyl group, I is an integer including 0,
and, X is xe2x80x94CH2xe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94SO2xe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94CH(C6H5)xe2x80x94, xe2x80x94C(C6H5)2xe2x80x94, not existing function group or chemical formula 4. 
other important applications of the present invention are resin sheet, resin clad copper, prepreg to be impregnated into and coated to the sheet type inorganic and organic substrate and resin sheet thereof and printed wiring board build-up printed wiring one obtained with heating and curing the said prepreg.
The present invention will be illustrated more in detail.
As illustrative examples of quinone compounds for present invention, 1,4-benzoquinone, 1,2-benzoquinone or 1,4-naphtoquinone can be mentioned. These of quinone compounds can be used alone or can be used together with, in addition, not intended to be limited to them.
As illustrative example of an organic phosphorus compound (b) having one active hydrogen atom bonded to phosphorus atom of present invention, 3,4,5,6,-dibenzo-1,2-oxaphosphane-2-oxide (abbreviated to HCA, a product of Sanko Chemicals Co., Ltd. Osaka, Japan), diphenylphosphineoxide or others can be mentioned. These of organic phosphorus compounds (b) can be used alone or can be used together with, in addition, not intended to be limited to them.
The reaction of quinone compounds with organic phosphorus compounds (b) having one active hydrogen atom bonded to phosphorus atom can be carried out, for example, by the methods disclosed in JP5-214068A, Zh. Obshch. Khim. 42(11) 2415-2418 (1972), which is a common chemical magazine of Russia, JP60-126293A, JP61-236787A or JP5-331179A. However, in the present invention, from 1.01 to 2 moles, desirably from 1.01 to 1.5 moles, more desirably from 1.01 to 1.4 moles of organic phosphorus compounds (b) having one active hydrogen atom bonded to phosphorus atom should be reacted with 1 mole of quinone compound, and when the molar ratio is over 2 moles, the reaction between epoxy group and organic phosphorus compounds (b) having one active hydrogen atom bonded to phosphorus atom takes place and consequently the large amount of component which does not have epoxy group, which is a bridging site to a hardener, is formed and decrease in its the heat resistance and adhesion. On the contrary, when the molar ratio of organic phosphorus compounds (b) having one active hydrogen atom bonded to phosphorus atom is smaller than 1.01 to 1 mole of quinone compound, these of two reactants do not proceed along with the suitable direction, and organic phosphorus compounds (b) or quinone compounds reminds. Especially, if there still reminds a sublimate quinone, it will affect physical properties such as heat resistance because the sublimate quinone does not have a reactive group that reacts with epoxy resin.
The reaction of quinone compound with organic phosphorus compounds (b) having one active hydrogen atom bonded to phosphorus atom is carried out as follows:
At first, an organic phosphorus compound (b) is dissolved in an inactive solvent, and then a quinone compound is added to the solution and heated with constant stirring so as to proceed the reaction completely. As illustrative examples of the inactive solvent, methanol, ethanol, isopropanol, chloroform, N,Nxe2x80x2-dimethylformamide, dioxane, ethyleneglycol, methoxypropanol, ethylcellosolve, benzene, toluene or xylene can be mentioned and any kind of solvents that can solve the organic phosphorus compound (b) can be used, and not intended to be limited to the mentioned solvents. However, among the quinone compounds, some kinds of them contain small amount of organic acid""s such as maleic anhydride or phthalic anhydride as an impurity, and when a solvent that has alcoholic hydroxyl group is used, these impurity acids react with alcoholic hydroxyl group of the solvent could results in forming the substance which does not take part in epoxy curing and it might decrease in heat resistance of cured epoxy product. Therefore, use of dioxane, benzene, toluene or xylene is more desirable. Quinone compounds are used in the form of powder or its solution. As above mentioned reaction of quinone and organic phosphorus compound is exothermic, required quantity of quinone is divided to small parting and added or by titration method of its solution to avoid quick rising of temperature. After its addition, the reaction mixture of the above quinone and organic phosphorus will keep for 1-4hours at the temperature range of 50 to 150xc2x0 C.
As an illustrative example of epoxy resins (C) represented by general formula 1 of this invention, Epotohto ZX-1027 (hydroquinone type epoxy resin, a product of Tohto Kasei Co., Ltd. Tokyo, Japan) can be mentioned, however not intended to be limited to this resin. As an illustrative example of epoxy resin (C) represented by general formula 2 of this invention, Epotohto ZX-1355 (1,4-dihydroxy naphtalene type epoxy resin, a product of Tohto Kasei Co., Ltd. Tokyo, Japan) can be mentioned, however not intended to be limited to this resin. As the illustrative example of epoxy resins (C) represented by general formula 3 of this invention, Epotohto YDF-170 and YDF-8170 (bisphenol F type epoxy resins, a products of Tohto Kasei Co., Ltd. Tokyo, Japan), Epotohto ZX-1251 (bisphenol epoxy resin, a product of Tohto Kasei Co., Ltd. Tokyo, Japan), Epotohto ZX-1201 (bisphenol fluorene type epoxy resin, a product of Tohto Kasei Co., Ltd. Tokyo, Japan), ESLV-80DE (diphenylether type epoxy resin, a product of Shin Nittetu Chemicals Co., Ltd. Tokyo, Japan) or ESLV-50TE (diphenylsulfide type epoxy resin, a product of Shin Nittetsu Chemicals Co., Ltd. Tokyo, Japan) can be mentioned, however not intended to be limited to these resins.
The epoxy resin (C) of general formula 1, general formula 2 and general formula 3 can be used alone or can be used together with each other, and the mixing ratio is from 20 to 45 wt. % to 100 wt. % of the phosphorus containing epoxy resin, desirably is from 20 to 43 wt. % and more desirably is from 20 to 41 wt. %. If the mixing ratio is smaller than 20 wt. %, adhesive strength, especially, adhesive strength between copper clad laminates will lower, and if the mixing ratio is over 45 wt. %, it will results in lowering heat resistance of cured product of the above composition.
As the illustrative example of novolac type epoxy resins of this invention, Epotohto YDPN-638 (phenol novolac type epoxy resin, a product of Tohto Kasei Co., Ltd. Tokyo, Japan), Epotohto YDCN-701, YDCN-702, YDCN-703, YDCN-704 (ortho-cresol novolac type epoxy resins products of Tohto Kasei Co., Ltd. Tokyo, Japan), Epotohto ZX-1071T, ZX-1270, ZX-1342, (alkylabon novolac type epoxy resins products of Tohto Kasei Co., Ltd. Tokyo, Japan), Epotohto ZX-1142L (naphtol novolac type epoxy resin a product of Tohto Kasei Co., Ltd. Tokyo, Japan), bisphenol novolac type epoxy resin, and aralkyl novolac type epoxy resin can be mentioned, however not intended to be limited to these resins.
The above mentioned novolac type epoxy resins can be used alone or can be used together with other ones or each other.
If the total content of the epoxy resins (C) of general formula 1, general formula 2 and general formula 3 is within the limit of from 20 to 45 wt. % in the above composition. Other kind of epoxy resins may be additionally used. As the other kind of epoxy resins, epoxies having more than 2 epoxy groups in 1 molecular resin, concretely, bisphenol type epoxy resin except general formula 3, resolcinol type epoxy resins, polyglycol type epoxy resins, trifunctional type epoxy resins, tetrafunctional type epoxy resins and novolac type epoxy resin can be mentioned, however, not intended to be limited to them.
The reaction between phosphorus containing organic compound (B), which can be obtained by reacting quinone compounds with organic phosphorus compounds (b) having one active hydrogen atom bonded to phosphorus atom, and epoxy resins (C) containing at least one selected from the groups composed of general formula 1, general formula 2 and general formula 3 can be carried out by well-known conventional method. That is, epoxy resins (C) is added to phosphorus containing organic compound (B), heated to reaction temperature of 100-200xc2x0 C., desirably 120-180xc2x0 C., with constant stirring so as to proceed the reaction completely. If the reacting rate is too slow, for the purpose to improve productivity, a suitable catalyst can be used to increase in productivity or to promote the reaction if required. As concrete examples of the catalyst, tertiary amine such as benzyldimethylamine, quaternary ammonium salts such as tetramethylammoniumchroride, phosphines such as triphenylphosphine, tris(2,6-dimethoxyphenyl)phosphine, phosphonium salts such as ethyltriphenylphosphoniumbromide, ethyltriphenyl phosphoniumiodide, or imidazole such as 2-methylimidazole or 2-ethyl-4-methylimidazole can be mentioned.
The desirable phosphorus content of phosphorus containing epoxy resin (A) of this invention is 1.2-4 wt. %, more desirably 2-3.1 wt. %. And the desirable phosphorus content of organic component in a flame retardant resin composition that contains phosphorus containing epoxy resin (A) is 0.5-4 wt. %, more desirably 1.5-3.5 wt. %, further, desirably 1-3 wt. %.If the phosphorus content of organic component in a flame retardant resin composition is smaller than 0.5 wt. %, it is difficult to maintain sufficient flame retardance, and if over 5 wt. %, heat resistance will be not expected more than one to meet increase in the phosphorous content, therefore, it is desirable to adjust the content of it to 0.5 to 4 wt. %.
The desirable epoxy equivalent of phosphorus containing epoxy resin (A) of this invention is 200-600 g/eq, more desirably 250-550 g/eq, further more desirably 300-500 g/eq. If the epoxy equivalent is smaller than 200 g/eq, the adhesion will be not sufficient, and if over than 500 g/eq, the heat resistance will lower, therefore, it is desirable to adjust it to 200 to 600 g/eq.
As hardener used for the compositions of this invention, conventional hardeners used for epoxy resins, for example, various kinds of phenol resins, acid anhydrides, amines, hydrazides or acidic polyesters can be used. These of hardeners can be used alone or can be used together with each other.
To the flame retardant epoxy resin composite that contains phosphorus containing epoxy resin of this invention, organic solvent may be used to adjust the viscosity. As usable organic solvent, amides such as N,Nxe2x80x2-dimethylformamide, ethers such as ethyleneglycol mono methyl ether, ketones such as acetone or methylethylketone, alcohols such as methanol or ethanol and aromatic hydrocarbons such as benzene or toluene can be used. One kind or more ones of these solvents may be mixed together with other one and can be blended to the epoxy resin in the limit of 30-80 wt. %.
To the compositions of this invention, a curing accelerator such as tertiary amine, quaternary ammonium salt, phosfine or imidazol can be blended if required.
As the fillers to be used in this invention, inorganic fillers such as aluminium hydroxide, magnesium hydroxide, talk, calcined talk, kaolin, titanium oxide, glass powder or silica balloons can be mentioned, and pigments can be blended. As the reason why the conventional inorganic filler is used, the improvement of impact strength of the above composition can be mentioned. And, when metal hydroxides such as aluminium hydroxide or magnesium hydroxide is used, suitable flame retardance can be mentioned even if the contents of phosphorus is low because it acts as flame retardancy promoting agent. The effect to the impact strength cannot be expected when the blending ratio of the said fillers is to the above composition smaller than 10%. However, if the blending ratio is over 150%, the adhesion of the said composition, which is an essential property for wiring board applications lowers. Furthermore, fibrous fillers such as glass fiber, pulp fiber, synthetic fibers or ceramics fibers or organic fillers such as fine particles of rubber or thermoplastic elastomers can be contained in said resin composition.
A resin sheet preparing method from above mentioned phosphorus containing epoxy resin compositions is illustrated as follows, however, the method to prepare a resin sheet is not restricted by the following description. That is, the above mentioned phosphorus containing epoxy resin compositions are coated over the surface of a carrier film that can not dissolved by the epoxy resin compositions, such as polyester film or polyimide film with desirable thickness of 5-100 xcexcm then hearted and dried up at 100-200xc2x0 C. for 1-40 minutes and formed to sheet shape. Namely, this method is usually called as casting method. If the surface of sheet to be coated is previously treated by a release agent before the coating of phosphorus containing epoxy resin compositions, the formed resin sheet can be easily released. The desirable thickness for the formed resin sheet is 5-80 xcexcm.
A resin clad copper preparation method from above mentioned phosphorus containing epoxy resin compositions is illustrated as follows:
As metal foil, copper, aluminium, brass, nickel, alloy of these metals or composite foil can be used. Desirable thickness of the metal foil to be used is 9-70 xcexcm. The method to produce metal sheet with resin from flame retardant resin compositions that contain phosphorus-containing epoxy resin and metal foil is not restricted by the above description. That is, for example, resin varnish of the said phosphorus containing epoxy resin composition whose viscosity has been adjusted by adding solvent is coated over one side of above mentioned metal foil by a roll coater. Then the coated surface is heated and dried up so as to make the resin composition semi-cured: (B staging), and to form a resin layer. To make resin composition semi-cured, for example, treatment by heating and drying for 1-40 minutes at 100-200xc2x0 C. can be mentioned. The desirable thickness of resin parts of resin clad metal is 5-110 xcexcm.
The prepreg prepared from above mentioned phosphorus-containing epoxy resin composition is illustrated as follows:
As the sheet shape substrate, woven cloth or non-woven cloth of inorganic fiber such as glass or organic fiber e.g. polyester, polyamine, polyacryric, polyimide or kebler can be used, however, not intended to be limited to them. Method to produce a prepreg from flame retardant resin compositions that contain phosphorus containing epoxy resin and a substrate is not restricted by the above description. The said prepreg can be obtained, for example, by impregnating the said substrate into resin varnish of said epoxy resin composition whose viscosity is adjusted by adding a solvent to it, and then the prepreg to make the resin component half hardened (B staging) by heating and drying up. For example, can be dried up by heating for 1-40 minutes at 100-200xc2x0 C. The desirable resin content in the solid prepreg is 30-80 wt. %.
The method to fabricate a laminated board using above mentioned resin sheet, resin clad metal foil and prepreg is illustrated as follows:
In the case to fabricate a laminated board using a prepreg, one or plural sheets of the prepreg are laminated and then a metal foil is arranged to one or both sides of the laminated prepreg, and the prepreg can be molded by a hot press molding to form one body. As metal foil, copper, aluminium, brass, nickel, alloy of mentioned metals or composite foil can be used. As the hot pressing condition for the laminated substance, a suitable curing condition should be selected for the above epoxy resin compositions. If pressing pressure is too low, as there will remind pores in a laminated board and lower the electric properties, it is desirable to press the board by the pressure which meets molding. For example, each molding conditions can be respectively settled as follows: that is, temperatures; 160-220xc2x0 C., pressures; 49.0-490.3 N/cm2 (5-50 kgf/cm2, hot pressing time; 40-240 minutes. Moreover, a build-up type printed wiring board can be fabricated by using obtained single layer laminated boards as inner material. In this case, at first, a circuit pattern is formed on the surface of laminated board by an additive process or a subtractive process, and then the circuit formed surface is treated by an acid and finally is treated to black oxide, thus the inner material is obtained. To one or both circuit formed surfaces of the said inner material, an insulated layer is formed using resin sheet, resin clad metal or prepreg, and then on the surface of insulated layer, an electro conductive layer is formed, thus the build-up type printed wiring board is obtained. In a case where insulated layer is formed using a resin sheet, a laminated substance is formed by arranging resin sheet on a circuit formed surface of plural inner materials, or, it is formed by arranging resin sheet between a circuit formed surface of inner material and a metal foil. Then the obtained laminated substance is molded by a hot press molding to be one body, and make the cured resin sheet an insulation layer, and then a multi layer inner material, can be obtained from an inner material, a metal foil that is an electric conductive layer and a cured resin sheet that is an insulating layer. As metal foil, the same materials that are used as a laminated board, which is used as an inner material, can be used. Further more, a hot press molding can be carried out by the same condition as the inner material forming one. In a case to form an insulating layer by coating resin on a laminated board, after coating phosphorus containing epoxy resin compound or flame retardant epoxy resin composition that contains phosphorus containing epoxy resin desirably by 5-100 xcexcm thickness on a circuit formed surface of outermost layer of inner material, heated and dried up at 100-200xc2x0 C. for 1-90 minutes, and then molded to form a sheet shape. The sheet can be formed by a method which is generally called as Casting method. The desirable thickness of the above laminated board is 5-80 xcexcm after its drying. To the surface of multi layer laminated board formed as above, via hole or circuit pattern is formed by a additive process or a subtractive process and a printed circuit board can be fabricated. When the above mentioned process is repeated using this printed circuit board as inner material, more complicated multi layered board can be fabricated. Further more, in a case to form an insulated layer using resin clad metal foil, a laminated material is formed by arranging the foil on a circuit pattern formed surface of inner material, so as the resin layer of resin clad metal to face the circuit pattern formed surface of inner material. The obtained laminate is molded by a hot press molding to form one body, and it makes the cured resin layer of resin clad metal foil an insulated layer, and the outer metal foil makes an electro conductive layer. The hot press molding can be carried out by the same condition as that of inner material forming. In a case to form an insulation layer using prepreg, one prepreg or a laminated material comprising plural prepregs is arranged to a circuit pattern formed surface of inner material, and a metal foil is arranged to the outer surface. Then the obtained laminated substance is molded by a hot press molding to form one body, and it makes cured prepreg an insulated layer, and the outer metal foil makes an electro conductive layer. As metal foil, the same material used in the laminated board, which is used as inner board, can be used. The hot press molding can be carried out by the same condition to that of inner material forming. To the surface of multi layered laminated board formed as above, via hole or circuit pattern is formed by a additive process or a subtractive process and then a printed wiring board can be fabricated. More complicated multi layer board can be formed when the above mentioned process is repeated using this printed wiring board as inner material.
The features of compositions of this invention and the laminated board obtained using said compositions are evaluated. The results show that the prepreg obtained by impregnating phosphorus containing resin compositions prepared by reacting phosphorus containing organic compound (B) obtained by the reaction in the range of molar ratio of 1.01 to 2 moles of organic phosphorus compounds (b) having one active hydrogen atom bonded to phosphorus atom and 1 mole of the said quinone compound, with at least one kind of epoxy resins (C) selected from the groups composed of general formula 1, general formula 2 or general formula 3 with the content of said epoxy resins (C) to be from 20 to 45 wt. % into the above composition, or with novolac type epoxy resins so as the content of said novolac type epoxy resins to be more than 20 wt. % in to the composition, and the laminated board obtained by curing the prepreg, which does not contain halogenated compound, indicates excellent flame resistance, and does not dissociate halogen at elevated temperatures, and further has good adhesion and excellent heat resistance.